1. Field of the Invention
The invention relates to an oscillator voltage source circuit, and more particularly to an oscillator voltage source circuit for reducing voltage deviation and controlling voltage easily.
2. Description of the Related Art
In general, a current-starved ring oscillator requires a constant current basing scheme or a feedback loop, so that current-controlled delay stages are charged or discharged, and delay units are formed in a feedback ring loop to generate oscillation.
A voltage source circuit of a ring oscillator is usually composed of a current source, transmission gates, and resistors, and charging and discharging operations are preformed through the resistors with different impedance. Current is generated by the current source according to a path which is manually selected. During duration of current generation, voltage source deviation occurs due to different number of transmission gates whereby the generated current passes, resulting in shift in an output frequency of the oscillator.
Thus, it is an important issue to solve the voltage source deviation and simplify charging/discharging processes.